Analysis and opinion by Christopher Soghoian, security and privacy researcher.

Wednesday, March 21, 2012

Firefox switching to HTTPS Google search by default (and the end of referrer leakage)

A few days ago, Mozilla's developers quietly enabled Google's HTTPS encrypted search as the default search service for the "nightly" developer trunk of the Firefox browser (it will actually use the SPDY protocol). This change should reach regular users at some point in the next few months.

This is a big deal for the 25% or so of Internet users who use Firefox to browse the web, bringing major improvements in privacy and security.

First, the search query information from these users will be shielded from their Internet service providers and governments who might be using Deep Packet Inspection (DPI) equipment to monitor the activity of users or censor and filter search results.

Second, the search query information will also be shielded from the websites that consumer visit after conducting a search. This information is normally leaked via the "referrer header". Google has in the past gone out of its way to facilitate referrer header based data leakage (which led to me filing a FTC complaint against the firm in 2010).

However, in October 2011, Google turned on HTTPS search by default for signed-in users, and at the same time, began scrubbing the search query from the non-HTTPS URL that HTTPS users are redirected to (and that subsequently leaks via the referrer header) before they reach the destination website:

Over the next few weeks, many of you will find yourselves redirected to https://www.google.com (note the extra “s”) when you’re signed in to your Google Account. This change encrypts your search queries and Google’s results page....

What does this mean for sites that receive clicks from Google search results? When you search from https://www.google.com, websites you visit from our organic search listings will still know that you came from Google, but won't receive information about each individual query.

At the time of the announcement, Google told the search engine optimization (SEO) industry (a community that very much wants to be able to continue to passively receive this kind of detailed user data) that the percentage of users whose search queries would be shielded would be a "single digit" -- and thus, at least 90% of Google users would still continue to unknowingly leak their search queries as they browse the web.

Shortly after Google's October announcement, search engine industry analyst Danny Sullivan told the SEO community that the days of referrer leakage were doomed:

By the future is clear. Referrer data is going away from search engines, and likely from other web sites, too. It’s somewhat amazing that we’ve had it last this long, and it will be painful to see that specific, valuable data disappear.

But from a consumer perspective, it’s also a better thing to do. As so much more moves online, referrers can easily leak out the location of things like private photos. Google’s move is part of a trend of blocking that already started and ultimately may move into the browsers themselves.

It looks like Danny was right.

Google's October 2011 decision to start proactively scrubbing search queries from the referrer header was a great first step, but a small percentage of Google's search users benefited. Now that Mozilla is switching to HTTPS search, hundreds of millions of Firefox users will have their privacy protected, by default.

The only surprising aspect to this otherwise great bit of good news is that the first major browser to use HTTPS search is Firefox and not Chrome. I reasonably assumed that as soon as Google's pro-privacy engineers and lawyers won the internal battle over those in the company sympathetic to needs of the SEO community, that Google's flagship browser would have been the first to ship HTTPS by default.

Just as it showed strong privacy leadership by being the first browser to embrace Do Not Track, Mozilla is similarly showing its users that privacy is a priority by being the first to embrace HTTPS search by default. For Mozilla, this is a clear win. For the Chrome team, whose browser has otherwise set the gold standard for security (and who have proposed and implemented a mechanism to enable websites to limit referrer leakage), this must be extremely frustrating and probably quite embarrassing. Hopefully, they will soon follow Mozilla's lead by protecting their users with HTTPS search by default.

(Just to be clear - the ultimate decision to enable HTTPS search by default was largely in the hands of Google's search engineers, who are responsible for dealing with the increased traffic. Mozilla's privacy team deserves the credit for pressuring Google, and Google's search engine team deserve a big pat on the back for agreeing to cope with encrypted searches from hundreds of millions of users.)

This is important, thanks for sharing. I wonder what will actually happen if your website is HTTPS also. Will you still see the keyword data if the Google user is not logged? Will you at least see the referrer?

This will also destroy the marketing of small businesses online. How are they supposed to plan how they appear to the search engines and how to get potentially more website views if they don't know how people are getting to their site in the first place?

@ Dave CullbertsonEven if you have a HTTPS website you won't be able to see the search query in analytics. It will turn up as unprovided. So for pro's in the SEO business it's a big strike as it will be harder to tell what keywords deserve most effort

Christopher Soghoian, Ph.D. is a Washington, DC based privacy and security researcher. He is the Principal Technologist in the Speech, Privacy and Technology Project at the American Civil Liberties Union.